Serendipity in Science: 35 years studying a tropical lake.

Lake Naivasha, Kenya, was once a rather unusual lake, but is becoming ordinary as it fills with alien species that are now commonplace and it becomes surrounded by developments and settlements. This presentation looks at 50 years of change in the lake through the 35 years we have been studying it and whether the knowledge of its limnology acquired, is any use in its management. A small (100-140km2) freshwater lake in a chain of mostly saline-al-kaline lakes running along the predominantly arid Eastern Rift Valley floor between Ethio-pia and Tanzania, Naivasha has always been essential to human existence and, since colo-nization in the lake 19th Century, drawn settlement. People had little impact on its ecology before the middle of the 20th Century, but an increasing list of deliberate introductions and accidental arrivals of alien species, that is still continuing, mean that the lake ecosystem is wholly novel beneath the water, yet can appear little changed above. In parallel to the alien invasion, agricultural and horticultural developments, bringing several hundred thousand people in new settlements, have markedly changed the lake hinterland and threatened its water quality. Intense subsistence cultivation throughout the catchment with increasing population reduce the quality and quantity of incoming river waters. Against these threats to its ecology, the lake responds with the most fickle hydrology imaginable, as a conse-quence of the Inter Tropical Convergence Zone. Seemingly about to become a dustbowl in 2009 through over-abstraction on top of a natural drought, that brought international experts to help write yet more management plans, the lake responded in heavy rains by rising by 2012 to a level last seen in 1969, with native species and high water quality re-turning. With such un-predictability and a near-impossibility of modeling, how useful is its science? Naivasha has been a great training ground for students and foreign scientists as a first ‘taste’ of Africa, but none of the science has generated any effective monitoring at all to guide sustainable management. Will this change? I shall give you a mentally easy pres-entation, to help you wake up, on the morning after the conference dinner.